冻结与非冻结环境对液-液雾化影响的实验研究

Experimental Study on Freezing or Non-Freezing Fluid Environmental Effect on Liquid-Liquid Atomization

水在低温冻结环境液体中雾化是液-液循环流化床制取流体冰技术的关键环节。今对常温非冻结环境或低温冻结环境中液-液雾化过程的射流与液滴形成特性进行了实验研究,提出了形成液滴的四种射流破碎方式,考察了冻结与非冻结环境中,滴流雾化向射流雾化转变的射流雷诺数,获得了射流雾化发生时随射流雷诺数的变化,射流破碎方式的转变规律、射流长度及其波动幅度与液滴平均粒径的变化规律。结果表明,射流液体在冻结或非冻结环境下雾化形成液滴的区域特性不一致,尤其是滴流雾化向射流雾化转变之后;射流液体在冻结环境中雾化只能形成单个液滴,其最小粒径的液滴形成在滴流向射流转变过程中,但是射流液体在非冻结环境下雾化可同时形成多个液滴,且形成液滴的粒径随射流雷诺数的增大而减小。

Water atomization in the freezing liquid environment is the key technique for fluid ice production by liquid-liquid circulating fluidized bed（LLCFB）.The characteristics of jet and drop formations of liquid-liquid atomization in freezing or non-freezing fluid environment were studied in a LLCFB.In the study,four typical jet breakup shapes relating to the drop formation were defined.The jet flow Reynolds number at which the mode of drop formation transits from dipping to jetting was investigated;and the rules of the changes of the jet breakup shapes,the jet length,its fluctuation extent and the average drop sizes of liquid-liquid jet atomization accompanying with the change of jet flow Reynolds number were obtained.The results show that,in the Rp/R-Reynolds graph,the region characteristics of droplets can be found;and under two different conditions of freezing and non-freezing fluid environments,the characteristics of drop formation in the same Reynolds number regions are unconformity,especially after the region of dripping switching to jetting.Single droplet is formed with all Reynolds numbers under freezing condition,and the minimum size of droplets appears during occurring dripping switching to jetting;whereas,multi-drops can be formed simultaneously under the non-freezing condition,and the drop sizes decrease generally with the increase of jet flow Reynolds number.